[Apakabar] Warning: message 1QMDom-0004XV-Ml delayed 24 hours

[Mail Delivery System]

This message was created automatically by mail delivery software.
A message that you sent has not yet been delivered to one or more of its
recipients after more than 24 hours on the queue on vm2548.vps.agava.net.

The message identifier is:     1QMDom-0004XV-Ml
The subject of the message is: =?koi8-r?B?/NTB0Nkg0sXHydPU0sHDyckgz8bG28/SwQ==?=
The date of the message is:    Tue, 17 May 2011 13:31:29 +0700

The address to which the message has not yet been delivered is:

  pimpampum at yandex.ru
    (ultimately generated from welcome at pimpam.ru)
    Delay reason: SMTP error from remote mail server after end of data:
    host mx.yandex.ru [87.250.250.89]: 451 4.5.1 The recipient <pimpampum at yandex.ru> has exceeded their message rate limit. Try again later. WF2O8Vpp-WF2SdBsF

No action is required on your part. Delivery attempts will continue for
some time, and this warning may be repeated at intervals if the message
remains undelivered. Eventually the mail delivery software will give up,
and when that happens, the message will be returned to you.